Pets are an integral part of many families. Dogs and cats are by far the most popular types of pets. Dogs and cats, like all animals, occasionally require access to the outdoors for exercise or to perform other biological functions. Traditionally, owners of pets opened a full size door each time the pet wanted to go outdoors and walked the pet on a leash. Eventually, some owners began fencing a portion of land so that the pet would be free to run within a confined space. Some owners found it convenient to leave the pet in the fenced in portion for most of the day, thereby avoiding repeated opening and closing of the outside door. However, in most climates, temperature variations from day to day could present a hazardous situation for a pet left outdoors.
In order to provide as much freedom as possible while still allowing the pet access into the regulated environment of the home, some pet owners installed small “doggy doors,” which the pet could open and close on their own. Most of the early “doggy doors” were simply openings in a wall covered with a flexible material that would give way when the pet passed through the opening. While accomplishing the function of giving the pet access in and out of the home, these early “doggy doors” did not seal well and thus were very energy inefficient. One solution to this problem was mounting a solid swinging door in the opening. Such a door is shown in FIG. 1. The door 10 includes a frame 12 surrounding an opening 14 in a wall of a home. One or more panels 16 are pivotably mounted within the frame 12. The panels 16 may swing in one or both directions and the panels 16 may be biased to a closed position by one or more springs (not shown). The solid panels provide better insulation and a more aesthetically pleasing appearance than the former flexible material doors.
Traditionally, such doors 10 were mounted in the frame 12 with a pivot pin 20 (FIGS. 2A-2B). The pivot pin 20 both located the panel 16 within the frame and provided a drive force (through a spring) to return the panel 16 to the closed position. A pivot pin having a square cross-section both locates the panel 16 and drives the panel 16 to a closed position by applying a force from a spring (not shown) to the panel 16 at one or more contact points 22. Other shapes of pivot pins 20 (FIGS. 2C-2D) may also provide contact points 22 to transfer the closing force from the spring to the panel 16.
The panels 16 are typically made of acrylic or other moldable materials, such as plastic. The contact points 22 (FIG. 2A) focus the drive force of the spring into a very small area of the panel 16. As a result, most prior art panels 16 eventually fail in the vicinity of the contact points 22 due to the repeated focused force from a pet pushing open the panel 16. Often, the pet will impact the panel 16 at full speed, thus producing an initial force that may be much greater than the spring force, causing even more stress within the panel 16 and damaging the pivot pin 20. Replacement of the damaged panel 16 or pivot pin 20 is expensive, time consuming, and physically difficult.